package com.king.nio.filechannel;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Arrays;

/**
 * Scattering：将数据写入到 buffer 时，可以采用 buffer 数组，一次写入【分散】
 * Gathering：从 buffer 读取数据时，可以采用 buffer 数组，依次读
 *
 * @author king
 * @date 2020/12/27 15:49
 */
public class ScatteringAndGatheringDemo {
    public static void main(String[] args) throws IOException {

        // 使用 ServerSocketChannel 和 SocketChannel 网络
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        InetSocketAddress inetSocketAddress = new InetSocketAddress(7000);

        // 绑定端口到socket, 并启动
        serverSocketChannel.socket().bind(inetSocketAddress);

        // 创建 buffer 数组
        ByteBuffer[] byteBuffers = new ByteBuffer[2];
        byteBuffers[0] = ByteBuffer.allocate(5);
        byteBuffers[1] = ByteBuffer.allocate(3);

        // 等待客户端连接(telnet)
        SocketChannel socketChannel = serverSocketChannel.accept();

        // 假定从客户端接收8个字节
        int messageLength = 8;

        // 循环的读取
        while (true) {
            int byteRead = 0;

            while (byteRead < messageLength) {
                long read = socketChannel.read(byteBuffers);
                // 累积读取的字节数
                byteRead += read;
                System.out.println("byteRead: " + byteRead);

                // 使用流打印，看看当前的 buffer 的 position 和 limit
                Arrays.asList(byteBuffers).stream().map(buffer ->
                        "position: " + buffer.position() + " limit: " + buffer.limit())
                        .forEach(System.out::println);

                // 将所有 buffer 进行 flip
                Arrays.asList(byteBuffers).forEach(buffer -> buffer.flip());

                // 将数据读出显示到客户端
                long byteWrite = 0;
                while (byteWrite < messageLength) {
                    long write = socketChannel.write(byteBuffers);
                    byteWrite += write;
                }

                // 将所有 buffer 进行 clear
                Arrays.asList(byteBuffers).forEach(buffer -> buffer.clear());

                System.out.println("byteRead： " + byteRead + " byteWrite: " + byteWrite + " messageLength:" + messageLength);
            }
        }
    }
}
